CN113196633A

CN113196633A - Device and method for pulling and twisting

Info

Publication number: CN113196633A
Application number: CN201980084630.2A
Authority: CN
Inventors: 马西莫·蓬齐奥; 鲁比诺·科尔比内利
Original assignee: ATOP SpA
Current assignee: ATOP SpA
Priority date: 2018-12-21
Filing date: 2019-12-19
Publication date: 2021-07-30
Anticipated expiration: 2039-12-19
Also published as: EP3900166A1; KR20210105901A; US20220060091A1; CN113196633B; WO2020127718A1

Abstract

The invention relates to a device (100) and a method for pulling apart the ends of the legs of a hairpin conductor arranged in a slot of a stator core, and to a device (200) and a method for twisting the ends of the legs of a hairpin conductor arranged in a slot of a stator core. The means (100) for pulling apart comprises at least one finger (111), preferably a plurality of fingers (111), for radially moving the ends of the legs of the hairpin conductors, the at least one finger (111) being arranged movable in a radially inward and a radially outward direction. The at least one finger (111) is arranged to be movable in an axial upward and an axial downward direction. The at least one finger (111) comprises at least one radially extending arm (101) and a separating member (102) arranged adjacent to an end of the arm (101), preferably a radially inner end. The separation member (102) is designed to be positioned between two ends (5a, 5b) of radially adjacent legs of a hairpin conductor pair (6, 6'). The finger (111) has a first section (104), preferably a radially inner section, adjacent to the separating member (102). The first section (104) has a first radial width (114) dimensioned to receive at least one pair (6) of foot ends and adapted to move the pair (6) of foot ends upon radial movement of the finger (111). The finger (111) has a second section (105), preferably a radially outer section, which does not overlap the first section (104). The second section (105) has a second radial width (116). The first radial width (114) is less than the second radial width (116), and wherein the second section (105) is dimensioned to receive without moving the at least one pair (6) of legs when the finger (111) is moved radially.

Description

Device and method for pulling and twisting

The invention relates to a device and a method for pulling apart (winding) the ends of the legs of a hairpin conductor arranged in a slot of a stator core, and to a device and a method for twisting the ends of the legs of a hairpin conductor arranged in a slot of a stator core.

The present invention generally relates to an apparatus and process for aligning wire conductor members inserted into slots of a core of an electrical machine.

It is known in the art to use apparatus and processes suitable for manufacturing stator coils for electric machines.

In a typical manufacturing scenario, the coil member is inserted into a slot of a core of an electrical machine. Pairs of wire conductors extending from the coil members, each conductor belonging to a coil member, are welded together. This type of coil member may be those having a forked shape, commonly referred to in the art as a "U-shaped coil member" or a "hairpin coil member". The hairpin conductor may be provided with two legs and a connection between the legs in general. Alternatively, the conductor may have only one leg or more than two legs.

A portion of the hairpin conductor, such as the connecting portion, extends axially outside the stator on one axial side of the stator core, while the legs extend from the slots on the opposite axial side of the stator core. By connecting two of the legs to each other a continuous conductor like a winding can be produced.

Stators wound with hairpin coil members are commonly used for electric or hybrid drive of motor vehicles.

The hairpin conductors may be preformed and/or may be pre-assembled into partial or complete nesting outside the stator core.

After the nest is inserted into the core, the ends of the hairpin conductors must be arranged so that the pairs to be connected are close to each other. In a further step, the feet may be pressed together and may be connected by welding.

The arrangement of the hairpin conductors is usually achieved by a twisting device. The twisting device typically comprises at least a first ring and a second ring, which are coaxial with each other and extend around the twisting axis. The ring includes a first annular array of pockets and a second annular array of pockets, respectively. The rings are relatively rotatable with respect to each other about the axis of torsion so as to assume at least first and second configurations in which the respective pockets of the first and second arrays are radially aligned with each other in pairs with respect to the axis of torsion.

The ends of the legs of the hairpin conductors protruding from the stator may be inserted into the pockets when the torsion device is in the first configuration. After rotating the ring to the second configuration, the two legs, which have been radially aligned in the first configuration, are radially offset from each other in the second configuration by a predefined pitch.

A fundamental requirement of the connection operation is the precise and repeatable positioning of the ends of the conductors with respect to each other and to the twisting device. For the subsequent welding process, the ends must be positioned closely together.

Increasing the hourly production of these stators requires reducing the time available for performing the placement and welding operations. This makes the positioning of the ends of the paired conductors less time.

The object of the present invention is to avoid the drawbacks of the prior art and in particular to provide a device and a method for quickly and accurately arranging the ends of a hairpin conductor in preparation for a welding step.

According to the present invention, these and other objects are solved with a device and a method according to the independent claims.

According to a first aspect of the invention, the device according to the invention is adapted to pull apart the ends of the legs of the hairpin conductors arranged in the slots of the stator core.

Typically, the hairpin conductor is inserted into a slot of the stator core, and the ends of the legs of the hairpin conductor axially protrude from the stator core. The slots are circumferentially arranged such that the pairs of legs of the conductors are radially aligned.

In order to allow the ends of the legs to be inserted into the pockets of the twisting device, the ends must be moved away from each other. This step is called unwinding. Preferably, the pair of leg ends belonging to a particular layer of the stator must be distanced with respect to the pair of leg ends of the adjacent layer. The layer comprises a first set of ends of the legs having a first distance from the stator axis and a second set of ends having a second distance from the stator axis, wherein two of the extension legs (one extension leg belonging to the first set and one extension leg belonging to the second set) are to be interconnected.

The device according to the invention comprises at least one finger for radially displacing the ends of the legs of the hairpin conductor. Preferably, the device comprises a plurality of fingers, such that the plurality of leg ends can be moved independently and/or simultaneously.

The at least one finger is arranged to be movable in a radially inward direction and a radially outward direction. The at least one finger is arranged to be movable in an axially upward direction and an axially downward direction.

The at least one finger includes at least one radially extending arm and a separating member.

Preferably, the arms are designed to be positioned between two circumferentially adjacent legs of the hairpin conductor.

The separating member is arranged adjacent to a (preferably radially inner) end of the arm.

The decoupling member may be connected to the arm. The arm and the separating member may be integrally formed.

The separating member may be arranged such that the arm and the separating member enclose an angle of 90 °. The separating member preferably has a circumferential extension. The circumferential dimension of the separating member preferably corresponds to the circumferential dimension of the legs of the hairpin conductors arranged in the stator.

The separating member preferably has an axial extension corresponding to the length of the ends of the legs, which ends are to be made available for connection.

The separation member is designed to be positioned between two ends of radially adjacent legs of the hairpin conductor pair.

The disconnecting member may comprise tapered axial ends allowing the disconnecting member to be introduced between the ends of the legs from the axial direction.

The fingers have a first (preferably radially inner) section adjacent the separating member.

Preferably, the first section is part of a space enclosed by the separating member and the arm.

The first section has a first radial width sized to receive at least one pair of legs and the first section is adapted to move the pair of legs as the finger moves radially.

Preferably, the first section is dimensioned to receive a pair of foot ends and the first section is adapted to move the ends.

Preferably, the first radial width is sized to snugly receive a pair of legs.

The radial extension of the legs of the conductor is in the range of 2mm to 5 mm. The circumferential extension of the legs of the conductor is also in the range of 2mm to 5 mm.

Thus, the first section has a radial width in the range of 4.5mm to 10.5 mm.

The finger has a second (preferably radially outer) section which does not overlap the first section.

Preferably, the second section is also part of the space enclosed by the separating member and the arm.

Preferably, a separating web is arranged between the first section and the second section. The second section may be part of the space enclosed by the web and the arms.

The second section has a second radial width, wherein the first radial width is less than the second radial width.

Preferably, the second section has a radial width in the range 11mm to 23 mm.

The radial length of the arm is greater than the sum of the radial width of the first section and the radial width of the second section.

Thus, the second section is dimensioned to receive at least one pair of ends.

Further, the second section is sized to receive at least one pair of legs, and the fingers are radially movable without moving the pair of legs received in the second section.

The first pair of leg ends located radially outward from the second and third pairs of legs may be received by the first section when the fingers have been brought to respective radial positions and have been moved axially such that the separating element is positioned between the first and second pairs of leg ends. The fingers may then move radially outward so that the first and second pairs of leg ends become further apart.

The finger may then perform an axial movement to release the first pair of legs from the first section. Now, the separating member may be positioned between the second and third pair of leg ends such that the second pair of ends is received in the first section and the first pair of ends is received in the second section. The second section has a sufficient radial width such that the first pair remains at its radial position when the fingers are moved radially to move the second and third pairs away. The arms may act as guide surfaces so that the circumferential position of the ends of the legs is also maintained.

Preferably, the radial width of the second section is large enough to receive at least two pairs of leg ends that are remote from each other.

The at least one finger is adapted to radially displace the ends of the pair of legs over a radial displacement distance.

Preferably, at least the radially outermost pair of legs is displaced in a radially outward direction.

Preferably, the radial length of the arm is greater than the sum of said radial movement distance and at least twice the radial extension of the end of the foot.

Since the ends of the pair of legs are arranged close to each other, the radial extension of the ends of the pair of legs corresponds to twice the radial extension of the ends of the legs.

In a preferred embodiment of the device, the at least one finger has a seat for axially receiving an end of a leg of the hairpin conductor.

The seat includes a first (preferably radially inner) compartment providing the first section and having a first radial compartment width dimensioned to receive the at least one pair of foot ends.

The first radial compartment width corresponds to a radial width of the first section.

The seat further comprises a second (preferably radially outer) compartment providing the second section and having a second radial compartment width. The second radial compartment width corresponds to the radial width of the second section.

Thus, the first radial compartment width is smaller than the second radial compartment width.

Preferably, the seat and the compartment are securely attached to the finger and may be integrally formed.

The separating member may be formed by one of the walls radially delimiting the first compartment, preferably by a wall arranged at the radially inner end.

A wall between the first compartment and the second compartment may form a separating web between the first section and the second section.

The finger may comprise two radially extending arms forming the side walls of the compartment.

The compartment is open at least in one axial direction towards the end of the foot. The lateral side walls of the compartment may provide lateral guiding surfaces which prevent circumferential movement of the ends of the legs during movement of the legs and during movement of the adjacent leg ends.

The compartment may comprise a floor or may be open in an axial direction facing away from the end of the leg.

When the finger is moved axially in the direction of the legs, at least one pair of legs may be received by the first compartment and at least another pair of legs may be received by the second compartment.

When the finger is moved radially, the ends of one pair of legs received in the first compartment move with the compartment while at least another pair of legs received by the second compartment do not move.

The first compartment may be sized to receive exactly one pair of ends.

The pair of leg ends may belong to one layer of the stator winding, wherein the connection is to be established in a further step.

The second compartment is sized to receive at least two pairs of ends. Thus, the device can be used to separate at least three pairs of legs. Up to four pairs of legs, radially aligned in a row, may be separated from each other while the last pair of legs remains unmoved by the device.

Each of the plurality of circumferentially arranged pairs having the same distance from the stator axis forms a layer. Thus, conductors may be prepared for welding for stator windings having up to four layers.

The fingers are rotatable in a circumferential direction about the stator axis and separate the ends of a row of radially aligned legs one from the other.

In a preferred embodiment, the machine comprises a plurality of annularly arranged fingers, and the fingers are independently movable. The fingers can be moved simultaneously so that the ends of the plurality of radially aligned legs can be pulled apart in the same step. Preferably, there is one finger for all radially aligned rows of leg ends.

The method according to the invention is suitable for pulling apart the ends of the legs of a hairpin conductor arranged in a slot of a stator core.

The method preferably uses an apparatus as described above and comprises the following steps.

A separating member connected to the (preferably radially inner) ends of the radially extending arms is positioned between the two ends of the radially adjacent leg pairs of the hairpin conductor. Preferably, the separating member is positioned by axially moving the arm and the separating member.

Radially moving at least one first leg pair of the hairpin conductor by radially moving the separation member.

The at least one first leg pair is disengaged from the decoupling member. Preferably, the pair of legs are disengaged by axially moving the arm and the disengagement member.

The separating member is radially moved to a radial position corresponding to the radial position of the at least one second leg pair while keeping the at least one first leg pair stationary.

The separating member is positioned, preferably by axial movement, adjacent to the second pair of legs, preferably on the radially inner side.

Preferably, the second leg pair is radially moved by radially moving the separating member while at least one first leg pair remains stationary.

In an advantageous embodiment, the further pairs of ends can be moved radially one after the other, while the already moved pairs of ends remain stationary.

In a preferred embodiment, the pairs arranged circumferentially around the stator axis are moved radially by a plurality of separating members in the same operating step.

In a preferred embodiment of the method, at least one first pair of legs is inserted into a first (preferably radially inner) compartment of the seat of the finger, said first radial compartment having a first radial compartment width.

The circumferentially extending wall of the first compartment serves as a separating member. The wall is preferably a radially inner wall.

At least one first pair of leg ends is radially moved by radially moving the fingers.

Preferably, the first pair of leg ends is moved in a radially outward direction away from the second pair of ends.

At least one first leg end pair is disengaged from the first compartment, preferably by axial movement of the finger.

The fingers are then radially moved to a radial position corresponding to the radial position of at least one second pair of leg ends radially adjacent the first pair of ends.

The at least one second leg end pair is inserted into the first compartment and the at least one first leg pair is inserted into a second (preferably radially outer) compartment having a second radial width greater than the first radial compartment width. The first end pair maintains its position.

By moving the fingers radially, the second leg end pair is moved radially while at least one first leg end pair remains stationary.

Preferably, the second pair of leg ends move in a radially outward direction while the first pair of ends do not move. The first and second pairs are closer to each other, but they have a greater distance than before the first end pair is moved radially.

Each step of radially moving provides precise positioning of one pair of leg ends, the positioning of the pair of leg ends being maintained during the further step of moving to position the further pair.

After the pulling-apart process, the pairs of leg ends are separated so that they are ready to be inserted into the pockets of the twisting device.

A second aspect of the invention relates to a device for twisting the ends of the legs of a hairpin conductor arranged in a slot of a stator core.

Preferably, the pairs of leg ends of the hairpin conductors have been separated by means and/or methods for pulling the ends apart as described above.

The means for twisting includes at least one pair of adjacent rings having a radially outer ring and a radially inner ring.

The inboard and outboard rings are directly adjacent, with no intermediate ring disposed between them.

At least one of the inner ring and the outer ring is movable in a circumferential direction relative to the other ring. Preferably, the inner ring and the outer ring are movable in circumferentially opposite directions.

The device may comprise further pairs of rings. Each pair of rings is used to position a layer of conductor of the stator winding.

Each of the inner and outer rings includes an open pocket for receiving an end of a leg of a hairpin conductor. Each open pocket is sized to receive exactly one leg end.

The open pocket in the radially outer ring has a radially outer wall and a radially inner open end.

The open pocket in the radially inner ring has a radially inner wall and a radially outer open end.

The opening pocket may have a side wall, and may also have a floor. A radial guide surface is present between the side walls of circumferentially adjacent open pockets.

When the inner and outer rings are circumferentially aligned, each open pocket of the inner ring forms a butt closed pocket with a corresponding open pocket of the outer ring for receiving a pair of leg ends. The radial guide surfaces of the inner and outer rings are also radially aligned and may contact each other at this location.

The abutting closure pockets each have a wall radially outward of the open pocket of the outer ring and a wall radially inward of the open pocket of the inner ring. The docking closure pocket may have sidewalls formed by sidewalls of the opening pocket.

The docking closure pocket is sized to snugly receive a pair of leg ends disposed adjacent to one another.

Since the docking closure pocket for receiving the ends of a pair of legs is formed by two open pockets, there is no separating wall between the pocket for receiving one of the pair of ends and the pocket for receiving the other of the pair of ends.

By moving at least one of the loops in the circumferential direction, the ends of the legs are bent such that each hairpin conductor has an additional pitch.

During twisting, the radial position of the ends of the legs received in the open pocket may be maintained by the walls of the open pocket and by the guide faces of the opposed rings.

The ends of the legs of the conductors of the respective layers may not only be immediately before welding, but may also have been brought closer together before twisting. Since the ends of the legs must be pulled apart anyway before insertion into the twisting device, the additional step of bringing the ends of one layer together after twisting is not necessary.

At least one of the rings may be circumferentially movable such that the open pocket of the inner ring and the open pocket of the outer ring form a first butt closed pocket in a starting position and a second butt closed pocket in an ending position.

Thus, in the starting position, the paired leg ends can be inserted into the docking closure pockets. After twisting, i.e. after moving at least one of the rings circumferentially, a new pair of leg ends is combined in the second butt closed pocket.

The degree of rotation of the ring defines the pitch of the conductors. For example, the number of open pockets between the end of the first leg and the end of the other leg of the same hairpin conductor plus one corresponds to the pitch of the conductors.

The method according to the invention is suitable for twisting the ends of the legs of the hairpin conductors in the stator core and uses the device for twisting as described above.

The method comprises the following steps.

At least one pair of leg ends of the hairpin conductor are inserted into a butt-closed pocket formed by the open pocket of the inner loop and the open pocket of the outer loop.

At least one of the inboard ring and the outboard ring is rotated circumferentially with one of the pair of leg ends retained in the open pocket of the inboard ring and one of the pair of leg ends retained in the open pocket of the outboard ring. The initially inserted pair of leg ends are moved away from each other and the T-shaped ends are bent by this machining step.

Preferably, pairs of leg ends arranged circumferentially with respect to the axis of the stator are inserted into corresponding pairs of abutting closure pockets formed by the open pockets of the inner ring and the open pockets of the outer ring. There may be more than one pair of inner and outer rings.

In a preferred embodiment of the method, each of the pairs of leg ends of the hairpin conductor is inserted into the butt close pocket and after the circumferential rotation a new pair of leg ends is arranged in the butt close pocket. Preferably, all the leg ends are part of a new pair.

Additional ends of special conductors may also be inserted into the mating pocket. Not all of the ends need be part of a pair. Also after twisting there may be abutting closed pockets that receive only one end of the legs of the conductor.

Thus, the ends of the legs are ready to be welded and form a winding.

The invention will be explained below with reference to the description of the embodiments and the corresponding drawings, in which:

FIG. 1 shows a perspective view of an apparatus for pulling apart the ends of the legs of a hairpin conductor;

FIG. 2 shows a perspective view of a detail of the means for pulling apart the ends of the legs of the hairpin conductor;

FIG. 3 shows another perspective view of a detail of the fingers of the device for pulling apart the ends of the legs of the hairpin conductor;

FIGS. 4a to 4c show schematic diagrams of method steps for pulling apart the ends of the legs of a hairpin conductor;

FIG. 5 shows a perspective view of an apparatus for twisting the ends of the legs of a hairpin conductor;

FIG. 6 shows a perspective view of a detail of a device for twisting the ends of the legs of the hairpin conductor;

fig. 7 shows a perspective view of further details of the means for twisting the ends of the legs of the hairpin conductor.

Fig. 1 shows a perspective view of an apparatus 100 for pulling apart the ends of the legs of a hairpin conductor.

The device comprises a plurality of fingers 111 for radially displacing the

ends

5a, 5b of the legs of the hairpin conductors (see fig. 3).

The fingers 111 are arranged circumferentially with respect to a system axis T corresponding to the axis of a stator (not shown in the figures).

The fingers 111 are arranged to be movable in the radial direction 106 and they are arranged to be movable in the axial direction 107.

The fingers 111 are independently movable.

Fig. 2 shows a perspective view of a detail of the device 100 for pulling apart the

ends

5a, 5b of the legs of the hairpin conductor (see fig. 3).

Each finger 111 includes at least one radially extending arm 101 and a separating member 102 disposed adjacent a radially inner end 108 of the arm 101.

The separating member 102 is designed to be positioned between the two

ends

5a, 5b (see fig. 3) of the radially adjacent legs of the hairpin conductor pair.

Each finger 111 has a first section 104 adjacent to the separating member 102, which is a radially inner section. The first section 104 has a first radial width 114 that is dimensioned to receive at least one pair of

legs

5a, 5b (see fig. 3) and is adapted to move the pair of

legs

5a, 5b (see fig. 3) when the finger 111 is moved radially.

Each finger 111 has a second section 105, which is a radially outer section, that does not overlap the first section 104. The second section 105 has a second radial width 116.

The first radial width 114 is less than the second radial width 116. The second section 105 is dimensioned to receive without moving at least one pair of

legs

5a, 5b (see fig. 3) when the finger 111 is moved radially.

A separating web 118 is arranged between the first section 104 and the second section 105.

Fig. 3 shows a perspective view of a detail of the finger 111 of the device 100 for pulling apart the

ends

5a, 5b of the legs of the hairpin conductor.

Each finger 111 has a seat 112 for axially receiving the

ends

5a, 5b of the legs of the hairpin conductor. The seat 112 comprises a first compartment 113, which is a radially inner compartment providing the first section 103 and having a first radial compartment width 114 dimensioned to receive one of the pairs of feet 6, and a second compartment 115, which is a radially outer compartment providing the second section 105 and having a second radial compartment width 116. The first radial compartment width 114 is less than the second radial compartment width 116.

The second compartment 115 is dimensioned to receive at least two pairs 6 of

ends

5a, 5 b.

Fig. 4a to 4c show schematic diagrams of the method steps for pulling apart the ends of the legs of the hairpin conductor.

The finger 111 is adapted to radially displace the

ends

5a, 5b of the pair of leg ends 6 over a radial displacement distance 117, said ends 5a, 5b preferably being at least the radially outermost ends.

The second radial width 116 is larger than the sum of said radial movement distance 117 and at least twice the radial extension 110 of the pair of leg ends.

The second radial width 116 is preferably in the range of 11mm to 23 mm.

The radial width 119 of the first section 104 is preferably in the range of 4.5mm to 10.5 mm.

The circumferential width 120 of the first and

second segments

104, 105 is preferably in the range of 2.5mm to 5.5 mm.

The radial length 103 of the arm 101 is greater than the sum of said radial movement distance 117 and at least twice the radial extension 110 of the pair of leg ends.

In a first step, the separating member 102 is positioned between the two ends of the radially adjacent leg pairs 6, 6' of the hairpin conductor (see fig. 4 a).

The first leg pair 6 of the hairpin conductor is radially moved by radially moving the separation member 102. The first pair of leg ends 6 is disengaged from the decoupling member 102. The separating member 102 is then radially moved to a radial position corresponding to the radial position of the at least one second leg pair 6' while keeping the at least one first leg pair 6 stationary (see fig. 4 b).

By moving the separating member 102 radially, the second leg pair 6' is moved radially while keeping the first leg pair 6 stationary.

Fig. 5 shows a perspective view of a device 200 for twisting the

ends

5a, 5b (see fig. 7) of the legs of a hairpin conductor.

The device 200 comprises a plurality of

pairs

201, 201', 201 "of adjacent rings 202, 203 (see fig. 6). The apparatus 200 comprises an actuating device 214 for independently moving the

rings

202, 203 in the

circumferential directions

204, 205.

Fig. 6 shows a perspective view of a detail of the device for twisting the

ends

5a, 5b of the legs of the hairpin conductor (see fig. 7).

The rings adjacent each

pair

201, 201', 201 "include a radially outer ring 203 and a radially inner ring 202.

The inner ring 202 and the outer ring 203 each comprise an

open recess

206, 207 for receiving the

ends

5a, 5b (see fig. 7) of the legs of the hairpin conductor.

The open pocket 207 in the radially outer ring 203 has a radially outer wall 208 and a radially inner open end 209.

The open pocket 206 in the radially inner ring 202 has a radially inner wall 210 and a radially outer open end 211.

When the inboard and

outboard rings

202, 203 are circumferentially aligned, each open pocket 206 of the inboard ring 202 forms an abutting closed pocket 212 with a corresponding open pocket 207 of the outboard ring 203. The abutting closure pockets 212 each have a wall 208 radially outward of the open pocket 207 of the outer ring 203 and a wall 210 radially inward of the open pocket 206 of the inner ring 202.

Fig. 7 shows a perspective view of additional details of an apparatus for twisting the ends of the legs of the hairpin conductor.

At least one of the inner ring 202 and the outer ring 203 is movable in a circumferential direction 204 relative to the

other ring

202, 203. Preferably, the inner ring 203 and the outer ring 202 are movable in circumferentially

opposite directions

204, 205.

When the inner and

outer rings

202, 203 are circumferentially aligned, each open pocket 206 of the inner ring 202 and the corresponding open pocket 207 of the outer ring 203 form an abutting closed pocket 212 for receiving the pair of ends 6 of the

legs

5a, 5 b.

The

rings

202, 203 are circumferentially movable such that the open pocket 206 of the inner ring 202 and the open pocket 207 of the outer ring 203 form a first butt closed pocket 212 in a starting position and a second butt closed pocket in an ending position. A new pair of leg ends is formed that are received in the second butt-closed pocket.

Claims

1. Device (100) for pulling apart ends (5a, 5b) of legs of a hairpin conductor arranged in a slot of a stator core, the device comprising at least one finger (111), preferably a plurality of fingers (111) for radially moving the ends of the legs of the hairpin conductor, wherein,

-the at least one finger (111) is arranged to be movable in a radially inward direction and in a radially outward direction;

-the at least one finger (111) is arranged to be movable in an axially upward direction and in an axially downward direction;

-said at least one finger (111) comprises at least one radially extending arm (101) and a separating member (102) arranged adjacent to an end of said arm (101), preferably a radially inner end;

-said separation member (102) is designed to be positioned between the two ends (5a, 5b) of radially adjacent legs of a hairpin conductor pair (6, 6');

-the finger (111) has a first section (104), preferably a radially inner section, adjacent to the separating member (102);

-said first section (104) has a first radial width (114) dimensioned to receive at least one pair of foot ends (6) and adapted to move said pair of foot ends (6) upon radial movement of said finger (111);

-and the finger (111) has a second section (105), preferably a radially outer section, which does not overlap the first section (104);

-the second section (105) has a second radial width (116);

-wherein the first radial width (114) is smaller than the second radial width (116), and wherein the second section (105) is dimensioned to receive without moving at least one pair of feet (6) when the finger (111) is moved radially.

2. The device according to claim 1, wherein a separating web (118) is arranged between the first section (112) and the second section (115).

3. The device according to one of the preceding claims, wherein the at least one finger (111) is adapted to radially move the ends of the pair of legs (6) over a radial movement distance (117), preferably the at least one finger (111) is adapted to radially move at least the radially outermost end of the pair of legs (6) over a radial movement distance (117), and wherein the radial length (103) of the arm (101) is larger than the sum of the radial movement distance (117) and at least twice the radial extension (110) of the pair of leg ends (6, 6').

4. Device according to one of the preceding claims, wherein the at least one finger (111) has a seat (112) for axially receiving the ends of the legs of the hairpin conductor, the seat (112) comprising a first compartment (113), preferably a radially inner compartment, providing the first section and having a first radial compartment width (114), the first radial compartment width (114) being dimensioned to receive at least one leg pair (6), and a second compartment (115), preferably a radially outer compartment, providing the second section and having a second radial compartment width (116), wherein the first radial compartment width (114) is smaller than the second radial compartment width (116).

5. The device of claim 4, wherein the first compartment (115) is sized to receive exactly one end pair (6).

6. Device according to one of the preceding claims 4 or 5, wherein the second compartment (115) is dimensioned to receive at least two end pairs (6, 6').

7. Device according to one of the preceding claims, wherein the machine comprises a plurality of annularly arranged fingers (111), and wherein the fingers (111) are independently movable.

8. A method for pulling apart ends (5a, 5b) of legs of a hairpin conductor arranged in a slot of a stator core, the method comprising the steps of:

-positioning a separating member (102) connected to the ends of radially extending arms (101), preferably the radially inner ends, between the two ends of a radially adjacent pair of legs (6, 6') of the hairpin conductor;

-radially moving at least one first leg pair (6) of a hairpin conductor by radially moving the separation member (102);

-disengaging said at least one first pair of foot ends (6) from said disconnecting member (102);

-radially moving the disconnecting member (102) to a radial position corresponding to the radial position of at least one second pair of legs (6') while keeping the at least one first pair of legs (6) stationary;

-and preferably, radially moving said second pair of legs (6') by radially moving said disconnecting member (102), while keeping said at least one first pair of legs (6) stationary.

9. The method according to claim 8, comprising the steps of:

-inserting at least one first leg end pair (6) in a first compartment (113) of a seat (112) of a finger (111), preferably a radially inner compartment, said first radial compartment (113) having a first radial compartment width (114);

-radially moving said at least one first pair of legs (6) by radially moving said finger (111);

-disengaging the at least one first pair of foot ends (6) from the first compartment (113);

-radially moving said finger (111) to a radial position corresponding to the radial position of at least one second leg end pair (6');

-inserting said at least one second pair of foot ends (6') into said first compartment (113) and said at least one first pair of foot ends (6) into a second compartment (115), preferably a radially outer compartment, having a second radial compartment width (116) greater than said first radial width (114);

-radially moving said second pair of foot ends (6') by radially moving said finger (111) while keeping said at least one first pair of foot ends (6) stationary.

10. System for preparing the ends of the legs of a hairpin conductor in a stator core for welding, comprising a device for pulling apart according to one of claims 1 to 7, and a twisting device.

11. A method for preparing the ends of the legs of a hairpin conductor in a stator core for welding, comprising the steps of the method according to one of claims 8 or 9, and the steps of the method of twisting.